Following a shooting at Marjory Stoneman Douglas High School in Parkland, Florida, that left at least 17 people dead, the 1999 shooting at Columbine High School is no longer the deadliest high school shooting. It's not even in the top 10 worst mass shootings in post-WWII American history. So what's changed since then?
Columbine marked a new style of mass shootings and new ways that both law enforcement and the public responded to them.
It wasn't the first school shooting — far from it. But it was one of the first to be covered on national television. And it was one of the last where police focused on surrounding a building instead of entering it to stop the shooter.
School security has also improved since 1999. More schools now lock or closely monitor their exterior doors. Faculty members undergo training, and students prepare for potential active shooter situations with drills.
But despite those changes, more than 150,000 students have experienced a school shooting since Columbine.
Additional reporting from Newsy affiliate CNN.